Multiparty-line telephone-exchange system.



G. BABCOGK. MULTIPARTY LINE TELEPHONE EXGHANGE SYSTEM.

APPLICATION FILED AUG.4, 1904.

Patented Oct. .20,` 1908.

InVE EL AEREI: BAEEDUL HUETLEX- UNITED STATES PATENT orricn.

GARRISON BABCOCK, OF ROCHESTER, NEW YORK, ASSIGNOR TO STROMBERG-UARLSON TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

MULTIPARTY-LINE TELEPHONE-EXCHANGE SYSTEM. p

Specification of Letters Patent.

Patented Oct. 20, 1908.

Application filed August 4, 1904. Serial No. 219,419.

To @ZZ who/m it may concern:

Be it known that 1', GARRIsoN Hancock,

citizen of the United States, residing at Rochester, in the county of Monroe and State of New York, have invented a certain new and useful Improvement in Multiparty- Line Telephone-Exchange Systems, of which the following is aV full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to vmulti-party telephone exchange systems and may be considered as an improvement over the system outlined in Patent No. 8255701, issued to me July 8rd, 1906.

The object of my present invention is to provide a multi-party line system which eniploys a central common battery for supplying the subst-ations with signaling current.

As will be hereinafter pointed out, my invention also contemplates improvements in the supervisory means whereby the proper cut-oit signals from the subscribers are ob! tained.

Other features of improvement are also addedand the system will be best understood by reference to the accompanying' drawings, in which:

Figure 1 illustrates two substations of different party lines to be connected together for conversation through a central exchange apparatus, and AFigs. 2 and 3 are detail views of a passing contact switch actuated by the substation switch hooks.

At each substation there is a polarized electromagnet 1 whose armature is provided with an arm 2 terminating in pawl mechanism 3. A ratchet wheel 4, mounted upon a shaft 5, is engaged by said pawl mechanism to step forward a switch arm 6, secured to the shaft. The end of the arm 6 travels over a ring 7, provided with a plurality7 of equally spaced holes 8, 8, into any one of which may be placed a contact pin 9, adapted to be engaged by the arm 6 upon its rotation about the ring 7. The contact l0 isdisposed above the ring, but insulated therefrom, and the arm G is normally in engagement with said contact. A relay 11 is connected in circuit between the ring 7 and the earth and controls an armature 12 to which is secured a switch arm 13. adapted, when the armature is attracted, to close contact with the contact spring 14, and a detent lever 15 serves to maintain a contact between the switch arm 13 and the spring lli. A receiver 16 norm ally rests on the switch hook 17, which engages the switch springs 18 to normally include the signal bells 19 in circuitbetween the switch arm 13 and ground, and a local transmitter circuit 2O is also associated with the switch springs 18. The switch hook is provided with an actuating stud 21 .for closing a passing Contact switch s only upon depression of the hook. This switch consists of spring a, connected with ground, and an actuating spring connected with thespring 1d and the normal contact 10.

Asseen in Figs. 2 and 8, the actuating spring is bent at its end to form a il -shaped cam c, the lower member Z of which is provided with an opening e, through which the stud 21 may pass upon elevation of the switch hook. Thus, as the hook is raised, the stud passes through the opening e and engages the under surface of the upper member ,f and the sprinoi will not engage the spring a.. Upon depressionof the switch hook, however, the stud engages the top surface of the cam and the switch will form a passing contact with the switch c. At each substation 1 provide an actuating cam g, of insulating material, secured to the shaft 5. switch 71V is opened when the arm 'G is in its normal position on the contact 10. An additional switch e' is normally closed and upon attractimi of the armature 12 by the electromagnet 11 opened. The switches 7i. and z" are connected serially in a local circuit including the receiver and, as will appear later', this local circuit locks out the receiver at all the undesired substations when conversation is carried on over the line.

,t the central station 1 have shown a cord circuit provided with a rear plug and a front plug 23, the rear plug engaging the spring jack connected with the line X to which is connected the calling subscriber O3, and the front plug being inserted in the spring jack connected with the line Y to which is connected the called subscriber C2. Selective keys 2d and 24, releasing keys 25 and 25, selective ringing keys 26 and 26', and metallic ringing keys 27 and 27 are respectively associated with the rear plug and the front plug of the cord circuit. Circuit changing switching mechanism 2S is associated with the rear plug and circuit changing mechanism. 28 is associated with the iti-ont plug. The circuit changing mechanism 2S consists oit an actuating sprine' 29 adapted to alternately engage springs BO and Ill, and the spring 32 is connected with, but insulated `trom, the spring 2i?) and alternately makes and. breaks contact with a switch spring 33. The circuit changing mechanism 28 consists of a' spring 29 adapted alternately to engage springs 30 and 3l and an actuating spring 32 is rigidly secured to, but insulated trom, i

the spring 25)', and alternately inalres and breaks contact with the spring 33. A cam 344; ot insulating material revolves between the actuating springs 29 and 32, whereby the circuit changing mechanisms are actuated to alternately short circuit the lines connected therewith and to connect with said lines a source ot current whereby current impulses are sent through the substation electromagnets l to step forward the switch arms 6. After the switch arms G at the de sired substations have traveled to engage the associated Contact pin 9, it is desired that cuirent be sent through the relay ll to telephonically connect the desired subscribers with the line. iit the central exchange l associate a plurality ot actuating buttons with each plug, these buttons being disposed in two rows, the trent row of buttons f1, f2, f3, etc. being associated with the front plug, while buttons r1, r2, 11,., etc. in the rear row are associated with the rear plug, there being sutlicient buttons in each row to provide for any number ot substations on a line, each substation being represented by a button. Below these buttons l dispose an endless conductor, which may be in the shape et' a band 36, adapted to travel over carrier wheels 37 and 38. The wheel 38 may be driven by weight mechanism 89, as shown, while the carrier wheel 37 is in driving relation with the cam Sel. Equally spacco contact ridges Ll0 project trom the band 3G and serve to engage and to restore the keys which have been depressed. The band 36 is continually connected with the negative side of the battery 35 through a conductor 4l and a wiper contact 4t2, while the buttons f1, etc. and r1, etc. are continually in connection with the earth through a conductor 43, contact springs illl and a resistance R.

Each line terminates at the central exchange in a spring jack 45. llhe tip spring lo ot the jack connected with line X is normally disengaged from the contact spring l-7, and the sleeve spring LS normally engages the contact spring at), and u pon insertion of a plug engages a contact spring 50. ln each jack a spring 5l is secured to, but insulated from, the sleeve spring 48, and

normally engages a contact spring 52. A line relay 53 is associated with each line and has an armature 54T adapted upon ntl traction to engage a spring 55 with a spring` 5l?. The cord circuit is divided into two conductively insulated sections by ctmdensers FJ und included serially in the cord strands, and bridged across the cord strands at each side et the condensers is a ipervisor;v relay 39 having an armature GO adapted upon attraction to engage spring (ll with a spring G2. Ai ringing circuit is supplied trom a source 63 which may be a source ot alten nating current or a polarity changer, and a main battery 34; supplies signaling current tor the substations and tor the exchange sig nals.

The operation ot the system is as tollows: Suppose the subscriber (l, on line il desires to converse with subscriber C: on line Y; he removes his receiver 'from the hoolt and depresses the switch hool to momentarily close the switch a. current will flow as lfollows: From the negative pole ot the battery (il al the central exchange to conductor 35, through the winding ot the line rela)v through the Contact springs fai-Sl and itt through the line limb GG, through conductor (3T, through switch arm (S, contact l0, conductor (i8 and through the switch s to ground and thence to the positive side oit the batti-)rid (Se. The armature 541e ot the line relay will thus be momentarily attracted but, upon such attraction, will engage the spring 55 with 'the spring 5G to close a local circuit. traced as follows: From the negative side ot the battery all, through conductor (35, the line relay winding, springs 52 and 5l` springs 55 and 56, and through condi'mtor (39 to the positive side oit the battery, und thus the line relay will remain energized and the operator will receive the signal and will thereupon insert the rear plug 22 into the spring jack. By so doing, she disengages the spring 5l from the spring 52 and the spring l trom the spring 49, tlierel'iy disrupting any circuit through the line relay winding, which becomes inert. Upon actuation oi lier listening lrey o and coiinection with the line ot her telephone set the operator may ascertain the desired subscriber and she thereupon inserts the trout plug 23 into the spring jack connecting with line She now actuates the selective lreys 24; and 24', as shown, and depresses actuating button corresponding with substation (l, and. actuating button ri, corresponding with substation C. One of the contactridges 4l() is disposed at the lett ot the actuating' buttons just in front of the button The starting key i-3 has been pulled upwardly, as shown. to release the contact ridge Ll()2 to allow the weight mechanismv to revolve the band 30 and at the same time to revolve the cani l. the cam in the figure being shown as just depressing the actuating spring 32', and when said actuating spring and the associl l t) ated spring 29' fully depressed to the right and the actuating spring 29l and the associated spring 32 are entirely retracted toward the right, the contact ridge 40 will be directlybelow the actuating button f1, and the circuit changing mechanism 28 serves to short circuit the line X through the following circuit: actuating spring 29, conductor 70, through the selective key 24 to the tip of the rear plug, thence through the substations on the line back tothe sleeve of the rear plu-g, to selective key 24, to conductor 71 and to spring 31, any static charge on the line being thus removed. The circuit changing mechanism 28', however, sends a positive impulse through the substations on line Y through the following circuit: actuating spring 32', conductor 7 2, selective key 24', conductor 73 to the sleeve of the front plug 23, through the substation apparatus on line C2 back to the tip oi' the front plug,

' through conductor 74, through the selective key 24', conductor 75', spring 29", spring 30', conductor 41 to the battery 35, conductor 76, conductor 77 and spring 33.'. This current is in a direction to actuate the electromagnets 1 at each of the substations on line Y, and the switch arm 6 at the substations will be stepped forward to be disposed over the first hole in the rino' 7.

t the next hall revolution of the cam, switch mechanism 28' will serve to short circuit the line Y and switch mechanism 28 will be actuated toV allow a current impulse to pass through the electromagnets 1 at the substations connected with line X and thus each line is alternately short circuited and alternately receives a positive impulse 'of current. After the second current impulse over the line Y, the switch arms will be disposed over the second hole which, at substation C2, is provided with a contact pin 9, the contact ridge 40 at the central exchange at the same time engaging the depressed button f2, and a current will ilow as follows: from the negative side of the battery 35 to conductor 41, wiper contact 42, contact band 33, contact ridge 40, actuating button f2 and the associated spring 44, conductor 43, resistance R to ground, and thence through the ground conductor 78 at the substation C2, through the relay 11, through conductor 79, through the ring 7 and pin 9 connected therewith, through arm 6, through conductor G7, through the line limb 6G to the sleeve of the front plug, to the conductor 7 3, through the selective key 24', conductor 72, actuating spring 3'2", spring 33', conductor 7 7 and through conductor 7 6 back to the positive side of the battery. The relay 11 at substation C2 is thus energized to attract its armature 12 and the switchlever 13 connected therewith into engagement with the contact 14, and the detent lever 15 drops to maintain this engagement. Upon the engagement of the detent 15 with the switch aun 13', the signal bells 19 which are normally grounded through switch mechanism 18 will. be connected with the sleeve line limb 66 through the conductor 80. Relays 11 at the other substations on line Y will not be energized as substation G2 is the only one in which the contact pin 9 is inserted in the second hole.

Upon the first impulse over the line,the cam g will move to close the switch h and at all the substations we have a local shunt 4circuit about the receiver which may be traced as follows: from the receiver 16, through the conductor 81, conductor S2, through the switch z, to conductor S3, through the switch z' to conductor 84, through springs ot' the switch mechanism 18 and through the secondary winding 85 back to the receiver. This shunt circuit about the receiver will he maintained at all substations excepting those desired for conversation, at which substations the arm 6 is in contact with the contact pin 9 to close a circuit through the relay 11 which attracts its armature to open the associated switch 2 to again open this shunt circuit and the receivers at the desired substations are connected with the line, and conversation may he carried on. Thus an effective locking out system is provided which absolutely cuts out from the undesired substations any means for hearing any of the conversation passing over the line. y

Upon a third impulse over the line X, the arm 6 at substation C3 will engage the contact pin 9I and at the same time ridge 4() will engage the depressed button r3 to close a circuit through the relay 11 and attraction of armature 12 will result to open the shunt circuit about the receiver and to connect substation C, with the line and with substation C2. In a similar manner as on line Y the remaining' subscribers on line X will be locked from the telephonie circuit.

Having thus set up the apparatus at the desired substations and locked out the apparatus at the other substations, the operator releases selective keys 24, 24' and actuates the calling key 26' connected with the plug 23, and the ringing circuit may be traced as follows: from the so-urce of ringing -current 63 to the conductor S5', through the ringing key 26', conductor 8G, through key 25', through selective key 24', through conductor 73, through the sleeve of the plug 23, through the sleeve line limb 66, through the-conductor 80, through detent lever 15, switch arm 13, signal bell 19, through springs on the switch mechanism 1S, to ground, from thence through the ground conductor 87 at the centra] exchange, through switch springs 88 and 89 associated with the callingA key 26', and through conductor 90 back to the ringing source.

A,\s the relay at substation C, is the only one on line Y which has been. energized, the corresponding signal bells 19 would be the only ones aliected upon actuation of ringing keys 26 and thus substation C, is selectively and independently signaled. rlhe subscriber at substation C2 now removes his receiver from the hook and is in communication with the subscriber at substation C, through the following circuit: From the receiver 16 at substation C, through conductor 81, through contacts 14 and 13, lever 15, conductor 80, line limb 66 to sleeve spring 48, through conduetor 7 3, through the middle spring of the ringing key 24 which is released through the inner spring of said key to the middle spring of the key 25, to the inner spring of said key, to conductor 86, through key 26', through key 27, to conductor 95, through conductor 96, keys 27 and 26, through conductor 97, through key 25, through key 24 which has been released, through conductor 99 to the sleeve member of the plug 22, to the sleeve springjack contact 48, to the conductor 66 of the line X, through conductor 80, lever 15 at substation C3, through contacts 13 and 14, to conductor 81, through the receiver 16 and through the switch hook springs to conductor 84 to line limb 106 back to the tip springjack 46 through conductor 105, through keys Q4 and 25, through keys 26 and 2i', through condenser 58, through keys 27, Q6, 25 and 24, through conductor T4, 'to the tip member of the plug 23, to the tip jack spring 46, to the limb 106 of line Y, to conductor 84 at substation G2, and through the switch hook springs back to the receiver 16.

Upon completion of conversation, both subscribers return their receivers to the hooks and the actuating studs on the hooks engage the corresponding switches s, as above described, to cause momentary closure thereof, and circuits will be closed through the correspending supervisory relays 59. For in stance, when switch s at substation C, is closed the circuit may be traced as follows: from the negative side of the battery 64, through conductor 65, through conductor 93, through winding 94 of the supervisory relay 59, through conductor 95, conductor 96, through the lower side ot the key 27, through conductor 96', through the lower side ot key 26, through conductor 97, through key 25, through the conductor 98, through key 24, to sleeve strand 99, through the sleeve of plug 22, to sleeve spring' 48, through sleeve line limb 66, through conductor 80, through detent lever 15, switch arm 13, spring 14, conductor 68, through switch s to ground and thence to the grounded side of the battery 64 at the central exchange. Upon this momentary flow of current through the above circuit, the armature of the relay will be attracted to engage its spring 61 with the spring 62, whereupon a local circuit will be closed through the winding 94 as follows: from the negative side ot the battery 64, through conductor 65, conductor 93, winding 94, springs 61 and 62, conductoi 100, springs 101 and 1,02 associated with the operators listening key 0 and through conductor 103 to the positive side of the battery 64. armature will thus remain attracted and the operator notified that conversation at substation (l, has been completed, and in the same manner completion of conversation at substation C, will be indicated by the supci visory relay F9. llt here the line resistance is not too great, the local circuits including the supervisory relay windings may he omitted as a line circuit will permanently include the supervisory relay when the switch hook is down, this circuit being traced as above but including the arm 13, signal bell 19 and switch mechanism 18, instead ot the passing contact switch s.

As the supervisory relays 59 and 59 are connected with Jthe cord strands at .opposite sides of the condensers 5'? and 58, the circuits through the relays will act independently ot' each other and cach subscriber independently signals the exchange operator. The conductor 93 connecting each relay winding through the battery 64 to earth is intcrniedi alely connected to the winding so that the proper amount ot impedance will be included at either side ot the conductor 93. whereupon a perfect balance of the system will he maintained. lt will also be noticed that upon actuation o tl the operators listening key o the positive side of the battery 6l will be disconnected from the local supervisory circuits, this preventing interference with conversation passing over the line should the operator at any time listen in.

Having thus received the cut ott signal trom both subscribers, the operator actuales the releasing keys 25 and 25 to send current through thesetting-np magnets 1 in a reverse direction to the setting-up impulse currents, and the following circuit through the` line X, for instance, may be traced: trom the positive side ot the battery through key to conductor 104, through key 24 to lip strand 105, through the tip ot the plug Q9 to the tip spring 46, tip line limb 106, through the electromagnets 1 connected with the line` back to the sleeveline limb 66,through sleeve spring 48 and sleeve of plug 22 to sleeve conductor 99, through key 24, conductor 98, key 25, through conductor 107 back to the negative side ot the battery t The direction ot o0. this current is opposite to the polarity ol" the setting-up impulses and, consequently` the armatures of the electromagnets 1 will be moved in opposite direction to withdraw the pawl mechanism 3 trom the toothed wht-els 4 and, as the shatts 5 are provided with spring mechanism, not shown, the arms 6 conce-9- will bev returned tof their normal positionto engage the contracts 10. Each shaft isalso providedwitha cam -arm 108, adapted upon release ofi the shaft to engage a cam surface 109 at the rearof the detentlever, and thus as thearrls 6 return to: their contacts'10, the cam arms 108 will` engage the detent levers 15 to disengagethese leversffrom the switch arms 13,1which are returned to their n-ormal positions by means of springs 110 and these operati-onsv cause the switch c' and /Lin the shunt circuit aboutthe receiver to be respectively closed and opened.

vThe sa-mecircuits maybe traced through the snbstati'ons connected with line Y and, having thus lpresumably 'released and restored'the apparatus at all the substations, the operator withdraws the plugs from the jacks. `li'fall the apparat-us at the substationshas been properly restored, there will be no actuation of the line signals there will be no ground connections at the substations. Should, however, the apparatus at any substation have failed to be properly restored and the switch arm 13 notreleased troni: the detent lever 15, there will still be a circuit to ground-from the sleeve line limb through the detent lever 15, switch arm 13, signal bells19 and' through the switch mechanism 18 and current will llowthrough this circuit to the ground connection vat the battery 6lat central, through this battery, throughthe conductor 65, the winding ot thel-ine relay 53, .through springs49 `and 48 back to the sleeve line limb and the local circuit heretofore 'traced will -be also closed throughthe linerelay winding and the operator vreceiving the signal knows innnediately that proper release and restoration has nottalren place and she again inserts the ther impulse ot' releasing current into the hne,'and thisis do-ne` until there is no actua-Y tion ofthe line signal upon withdrawal ofr the plug.A 1t may, however, happen that owing' to the high combined resistance ot the bell atna substation and the line, there `will be insufficient energy/lowing through the winding ont the linev relay to canse attraction o-its armature and, consequently, the operator will not Vbe signaled leven'lhough the proper restoration has not been accomplished.A :To insure a signal tothe operator upon such non-release, I provide an auxiliary relay which may be of lthe kind described in the (Jo-pending application of Villiam vKaisling, 'Serial No. 182,390, filed November 23, 1903, which relay consists ot a permanent magnet 112, an armature 113 andfa switch 114C actuated by the armature, a magnetic brake 115 serving to impede theattraction of the armature-in the direction, in this particular ca'se,`to open the switch 1141, the operation ot' this.relay-being-more inin'u-tely vdescribed in the above ret'erred to copending application.

VThe armature 113 is provided with a winding 116 connected with the alternate contact. springs 47 and of the spring jack and uponinsertion of the plug 22 in the jack, this windingwill be bridged across the line limbs and also across the battery 35 upon actuation of selective key 24. Upon selective current impulses passing into the line from the battery 35, current will flow through the winding 116 to polarize the armature which will be'attracted by the permanent magnet core 112 to close the switchllt. As the operator upon completion of conver- `sation -actuates the releasing key 25 to send releasing current ot' opposite polarity into the line `from the battery 35, the armature t113 will be oppositely polarized and lthe tendency will be for the magnet 112 to attract the armature to open the switch 114, and with this polarity oi' the armature, the brake 11'5 will be attracted to retard the movement ol the armature and, consequently, a great deal of energy willbe required to cau'se opening of the switch 114. k0n the other hand, the electromagnets 1 atthe substantious are of delicate adjust- .ment and require very little energy for actuation and the presumption is that ifthe `releasing current is sutliciently strong to actuate'the auxiliary relay, it will be more than strong eno-ugh to have actuated all the .eleetroma-'gnets `1 to cause proper release thereoftoI allow perfect restoration ofthe substation apparatus. It the auxiliary relay has not been su'liiciently energized to open the switch 114, the operator, upon withdrawal of the plug, will be notified by :actuation of the armature 5l, since a local circuit Hows as follows through the winding` ofthe'line relayzfroin the positive side of the battery 64, through conduct-0r 117, lswitch 1141, springs 51 and 52 of the spring jack, conductor 118, through the line relay winding and through conductor back to the negative side of the battery, and she must reinsertthe plug and send a further releasing impulse over the line. It the energy is then sutcient to actuate the auX- iliary relay to open the switch 1111, any circuit through the line relay 53 will be opened land the operator is certain that proper restoration has taken place.

l; thus provide a system in which the apparatus at the substations on two lines may Xbe practically operated at the same time from the central exchange and in which only the desired substations are connected for conversation, the others being absolutely locked out. By means of the double supervisory signal system, the operator has independent supervision of each line and, by means of thereleasing and restoring supervisollyapparatus, the operator is at all times certain that the substation apparatus has been restored to its proper normal condition, all the setting-up, locking-out and supervisory apparatus being actuated from a central common source of current.

As many modifications may be made witl out departingl trom the spirit of the invention, l do not wish to be limited to the precise arrangement as shown, but

Having described my invention I wish to secure by Letters Patent the following claims l. .lin a telephone exchange system, the

'combination with a central exchange, of a telephone line leading therefrom and terminating in a sub-station, a source of current at the exchange, a line signal at the exchange associated with said line, a normally open passing contact switch at the sub-station a sociated with a receiver hook, said passing contact hook being adapted to momentarily close a circuit` through said source of current and said line signal upon depression of said receiver hook, local means at the central exchange for maintaining actuation of said line signal, and switch mechanism at the sub-station adapted to be actuated from the central exchange te cause said passing contact switch to be disconnected from said line circuit..

2. In a telephone exchange system, the combination with a central exchangefof a telephone line leading therefrom and terminating in a sub-station, a source of current at the exchange, a line signal at the central exchange associated with said line, a normally open passing contact switch at the sub-station associated with a receiver hook, saidlpassing contact switch being adapted to momentarily close a circuit through said source of current and said line signal upon depression of the receiver hook, local means at the central. exchange for maintaining ac tuation of said line signal, switch mechanism at the sub-station operated from the central station to disconnect said passing contact switch from the line circuit, signal bells at the sub-station, and switch mechanism for connecting said signal bells with the line circuit.

3. ln a telephone exchange system, the combination with a central exchange, of a telephone line extending therefrom and terminating in a substation, a source ot current at the central exchange, a line relay for said telephone line, a line signal controlled by said line relay, a normally open passing contact switch at the sub-station associated with a receiver hook, said passing contact switch being adapted to momentarily close a circuit through said source of current and said line signal upon depression et said receiver hook, local meansat the central ex change for maintaining actuation of said line signal, switch mechanism at the substation operated from the central exc-hang@ tor disconnecting said passing contact switch 2rom. the line, and a relay at the sub-station controlled by said switch mechanism, said relay controlling switch springs .vherebythe signal bells 'lor the sub-station ma\v be connected with the line circuit.

l. ln a telephone exchange system, the combination with a central exchange, ot a telephone line extending therefrom and terminating in a substation, a source ot current at the central exchange, a line relay l'or said telephone line, a line signal controlled by said line relay, a passing contact switch at the sub-station associated with a receiver hook, said passing contact switch being adapted to momentarily close a circuit through said source ot current and said line relay only upon depression ot the reiei 'er hook, local. means at the central exchange tor maintaining actuation ot said line signal` switch mechanism at the substation controlled from the central exchange iter disconnecting said passing contact switch from the line, signal bells at the substation, and a relay controlling switch springs whereby said signal bells f' be connected with the circuit, the circuit through .said relay being controlled by said switching device whereby said signal bells may be connected with the line after said passing contact switch has` been disconnected therefrom.

5. In a telephone exchange system, the combination with a central. exchange, ot a telephone line leading' therefrom and ternii nating in a substation, a cord circuit at the central exchange, a source ot current at the central exchange connected with said tele-- phone line, a line signal at the central ci; change for said telephone line, switching mechanism at the substation, a receiver hoot: at the substation, a passing contact switch controlled by said switch hook, a line circuit normally including' said source ot current, said line signal, said switching apparatus and said passing contact switch to bc momentarily closed upon depression ol said. re eeircr hook, whereby said line signal i s actuated, local means at the central exchange tor maintaining actuation et said line signal, means upon connection oi the cord circuit with said telephone line for causing said line signal'to become inert, a signal hell at the substation normally disconnected. trom said line circuit, and .means :tor actuating said switching mechanism trein the central ex change to cause sai-d passing contact switch to be disconnected troni said line circuit and to cause connection with said line circuit ot said substation signal bell, said signal bell then controlling the continuity of said line circuit upon disconnection ot said cord cir cuit troni said telephone line.

6. ln a telephone exchange system, the combination with a central exchange, ot a plurality of telephone lines leading therefrom, each connecting with a plurality of snbstations, a cord circuit at the central exchange for connecting lines together, a source lof current at the central exchange for supplying signaling current to the substations, a line signal for each telephone line, a passing contact switch at each substation adapted to be closed only upon depression of the associated receiver hook to momentarily close a line circuit through the corresponding line signal, Vlocal means for each line signal for maintaining actuation thereof, connection of the cord circuit with the lines causing the corresponding line signals to become inert, means for dividing the cord circuit into two conductively insulated parts, and a supervisory relay for each part connected in bridge of the cord strands, said supervisory relays being momentarily energized upon Vactuation of the corresponding substation passing contact switch upon depression of the receiver hook, and local circuits for the supervisory relays for maintaining actuation thereof.

T. In a telephone exchange system, the combination with a central exchange, of telephone lines leading therefrom, each connecting with a plurality of substations, a cord circuit at the central exchange for connect- 'ing lines together, a common source of current at the central exchange for supplying signaling current to all the substations, a line signal for each telephone line normally connected with one line limb and a third conductor, a passing vcontact switch at each substation connected with said line limb and the third conductor, actuation of said contact switch upon depression of an associated receiver hook causing momentary closure of a line circuit containing said source of current and the corresponding line signal, a local circuit for each line signal for maintaining actuation thereof, means for dividing the cord circuit into two conductively insulated parts, a supervisory signal for each part bridged across the cord strands, a wind ing of each supervisory signal connected with the third conductor, connection of the cord circuit with the lines causing the corresponding line signal to become inert and the corresponding supervisory signal to be momentarily actuated upon depression of the corresponding receiver hook, and a local circuit for each supervisory signal for maintaining actuation thereof.

S. In a telephone exchange system, the combination with a central exchange, of a telephone line leading therefrom and terminating in a substation, a cord circuit at the central exchange, a line relay normally connected with the telephone line adapted to be actuated upon actuation of substation apparatus, connection of said cord circuit with the line causing said line signal to be disconnected therefrom, an auxiliary relay normally 4connected with the line, means connected with the cord circuit for sending current into the line whereby said auxiliary line relay is energized, switching mechanism closed by said auxiliary relay upon energization thereof, and a local circuit including said switching mechanism and the winding of said line relay upon disconnection of the cord circuit from the line.

9. In a telephone exchange system, the combination with a central exchange, of a telephone line leading therefrom and terminating in a substation, a spring jack connected with the telephone line at the central exchange, a line relay normally connected with said telephone line through spring jack contacts, an auxiliary line relay normally disconnected from the line, a switch controlled by said auxiliary relay, a local circuit adapted -to include said switch and the line relay winding, a cord circuit at the central exchange, connection of said cord circuit with the spring liack causing disconnection of the line relay, and connection with the spring jack and line of said auxiliary relay, contacts of said spring jack partly controlling said local circuit, and means associated with the cord circuit for sending current impulses through the spring jack, whereby said auxiliary line relay is energized to close its associated switch and the local circuit through said switch, disconnection of the cord circuit from the jack causing said spring' jack contacts to completely close the local circuit, whereby said line relay is actuated.

10. In a telephone exchange system, the combination with a centra-l exchange, of a telephone line extending therefrom and tervinitiating in a substation, a spring jack connected with the line, a line relay normally connected with the line through said spring jack, a line signal controlled by said line relay, actuation of substation apparatus causing actuation of said line relay to display its signal, a polarized auxiliary line relay normally disconnected from said spring jack. a switch controlled by said auxiliary line relay, a local circuit adapted to include said switch and the winding of said line relay, jack contacts normally included in said local circuit, a cord circuit at the central exchange provided with plugs, insertion of a plug into said spring jack causing said line relay to be disconnected from said line, said auxiliary relay to be connected with said cord circuit and said local circuit to be opened at said spring jack contacts, means associated with the cord circuit for sending current impulses of one polarity through said spring ack and into the line to actuate substation apparatus and to energize said auxiliary line relay to close the associated switch included in the local circuit, and additioual means associated with said cord circuit for sending currents of opposite polarity through the spring jack and into the line, whereby said auxiliary linerelay is energized to open the associated switching mechanism and to open the local circuit at this point, whereby the line relay will not be energized upon Withdrawal of the plug from the spring jack.

ll. In a telephone exchange system, the combination with a central exchange, of a telephone line extending therefrom and terminating in a sub-station, a source of current at the central exchange for supplying signaling current to said telephone line, a line signal at the central exchange for the telephone line, a passing contact switch at the sub-station associated with the receiver hook adapted to momentarily close a circuit through said source of current and said line signal, said. passing contact switch consisting of a 'contact spring and an actuating spring, said actuating spring being provided with a V -shaped head for engagement with a stud on said receiver hook, said stud being adapted upon depression of said receiver hook to pass about said Vshaped head whereby said actuating spring may make contact with said contact spring, and being adapted to pass through said V-shaped head when said hook is raised whereby effectual actuation of said actuating spring is prevented.

l2. ln a telephone exchange system the combination with a central exchange, of a telephone line extending therefrom and terminating in a sub-station, a source of current at the central exchange7 a line signal at the central exchaiige for the telephone line, and a passing' contact switch at the substation associated with the switch hook for soi, eee

momentarily closing the circuit through said line signal., said passing contact switch consisting of a contact spring and an actuating spring,- said actuating spring having a 'tfshaped cam head for engagement with a stud on said receiver hook, said stud being adapted upon depression of said hook to pass about said V-shaped cam whereby said actuating spring is brought into engagement with said contact spring, and being adapted when said hook is raised to pass through a slot in said spring whereby it may pass through the il-shaped head, thereby preventing effectual actuation of said actuating spring.

13. In a telephone exchange system, the combination with a central exchange, of a telephone line extending therefrom and terminating in a sub-station, a source of current at the central exchange for supplying current to the telephone line, a line signal at the central exchange for the telephone line4` a contact spring at the sub-station, an actuating spring associated with said Contact spring, and a cam head for said actuating spring, said cam head having a cam surface to be engaged by a stud on the receiver hook at the sub-station upon depression thereof whereby said actuating spring is brought` into engagement with said contact spring, said stud being adapted when said hook is raised to pass through a slot in the cam head whereby said actuating spring is prevented from being effectually actuated.

In witness whereof, l hereunto subscribe my name this 26th day of July A. D. i90-i.

GAR-EUSON BAB UU (lli.

Witnesses S. A. Cnos'roN, FREDERICK W. Corr. 

